Napa Valley in the Bay Area in California, is the main wine growing region of the United States of America and one of the major wine regions of the world. It is also known for its gourmet restaurants, cafes, and spa-treatment centers. Napa Valley is one of the most popular tourist attractions in California with more than five million visitors come each year. Peak times are the summer months and the harvest "crush" during September and October. Napa Valley is home to more than two hundred wineries. With wine as a focus, great dining naturally emerged to complement it. The Napa Valley enjoys a Mediterranean climate. Summer is marked by warm to hot, sunny days, cool nights, and little to no rain. Winter is mild, and is characterized by frequent rain and occasional frosts. In prehistoric times, the valley was inhabited by the Patwin Native Americans, with possible habitation by Wappo tribes in the northwestern foothills. Most villages are thought to have been constructed near the floodplains of watercourses that drain the valley. Their food consisted of wild roots, acorns, small animals, earthworms, grasshoppers, and bread made from crushed California buckeye kernels. In winter they would construct huts made of tree branches. In summer they camped near rivers and streams. In winter months, they were half clad in wild animal skins and at other times they wore no clothing. The maximum prehistoric population is thought not to have exceeded 5000 persons.